# Part of DTCloud. See LICENSE file for full copyright and licensing details.

import base64
import binascii
import contextlib
import hashlib
import io
import itertools
import logging
import mimetypes
import os
import psycopg2
import re
import uuid

from collections import defaultdict
from PIL import Image

from dtcloud import api, fields, models, SUPERUSER_ID, tools, _
from dtcloud.exceptions import AccessError, ValidationError, UserError
from dtcloud.tools import config, human_size, ImageProcess, str2bool, consteq
from dtcloud.tools.mimetypes import guess_mimetype
from dtcloud.osv import expression

_logger = logging.getLogger(__name__)


class IrAttachment(models.Model):
    """Attachments are used to link binary files or url to any openerp document.

    External attachment storage
    ---------------------------

    The computed field ``datas`` is implemented using ``_file_read``,
    ``_file_write`` and ``_file_delete``, which can be overridden to implement
    other storage engines. Such methods should check for other location pseudo
    uri (example: hdfs://hadoopserver).

    The default implementation is the file:dirname location that stores files
    on the local filesystem using name based on their sha1 hash
    """
    _name = 'ir.attachment'
    _description = 'Attachment'
    _order = 'id desc'

    def _compute_res_name(self):
        for attachment in self:
            if attachment.res_model and attachment.res_id:
                record = self.env[attachment.res_model].browse(attachment.res_id)
                attachment.res_name = record.display_name
            else:
                attachment.res_name = False

    @api.model
    def _storage(self):
        return self.env['ir.config_parameter'].sudo().get_param('ir_attachment.location', 'file')

    @api.model
    def _filestore(self):
        return config.filestore(self._cr.dbname)

    @api.model
    def _get_storage_domain(self):
        # domain to retrieve the attachments to migrate
        return {
            'db': [('store_fname', '!=', False)],
            'file': [('db_datas', '!=', False)],
        }[self._storage()]

    @api.model
    def force_storage(self):
        """Force all attachments to be stored in the currently configured storage"""
        if not self.env.is_admin():
            raise AccessError(_('Only administrators can execute this action.'))

        # Migrate only binary attachments and bypass the res_field automatic
        # filter added in _search override
        self.search(expression.AND([
            self._get_storage_domain(),
            ['&', ('type', '=', 'binary'), '|', ('res_field', '=', False), ('res_field', '!=', False)]
        ]))._migrate()

    def _migrate(self):
        record_count = len(self)
        storage = self._storage().upper()
        for index, attach in enumerate(self):
            _logger.debug("Migrate attachment %s/%s to %s", index + 1, record_count, storage)
            # pass mimetype, to avoid recomputation
            attach.write({'raw': attach.raw, 'mimetype': attach.mimetype})

    @api.model
    def _full_path(self, path):
        # sanitize path
        path = re.sub('[.]', '', path)
        path = path.strip('/\\')
        return os.path.join(self._filestore(), path)

    @api.model
    def _get_path(self, bin_data, sha):
        # retro compatibility
        fname = sha[:3] + '/' + sha
        full_path = self._full_path(fname)
        if os.path.isfile(full_path):
            return fname, full_path        # keep existing path

        # scatter files across 256 dirs
        # we use '/' in the db (even on windows)
        fname = sha[:2] + '/' + sha
        full_path = self._full_path(fname)
        dirname = os.path.dirname(full_path)
        if not os.path.isdir(dirname):
            os.makedirs(dirname)
        # prevent sha-1 collision
        if os.path.isfile(full_path) and not self._same_content(bin_data, full_path):
            raise UserError(_("The attachment collides with an existing file."))
        return fname, full_path

    @api.model
    def _file_read(self, fname):
        assert isinstance(self, IrAttachment)
        full_path = self._full_path(fname)
        try:
            with open(full_path, 'rb') as f:
                return f.read()
        except (IOError, OSError):
            _logger.info("_read_file reading %s", full_path, exc_info=True)
        return b''

    @api.model
    def _file_write(self, bin_value, checksum):
        assert isinstance(self, IrAttachment)
        fname, full_path = self._get_path(bin_value, checksum)
        if not os.path.exists(full_path):
            try:
                with open(full_path, 'wb') as fp:
                    fp.write(bin_value)
                # add fname to checklist, in case the transaction aborts
                self._mark_for_gc(fname)
            except IOError:
                _logger.info("_file_write writing %s", full_path, exc_info=True)
        return fname

    @api.model
    def _file_delete(self, fname):
        # simply add fname to checklist, it will be garbage-collected later
        self._mark_for_gc(fname)

    def _mark_for_gc(self, fname):
        """ Add ``fname`` in a checklist for the filestore garbage collection. """
        assert isinstance(self, IrAttachment)
        fname = re.sub('[.]', '', fname).strip('/\\')
        # we use a spooldir: add an empty file in the subdirectory 'checklist'
        full_path = os.path.join(self._full_path('checklist'), fname)
        if not os.path.exists(full_path):
            dirname = os.path.dirname(full_path)
            if not os.path.isdir(dirname):
                with contextlib.suppress(OSError):
                    os.makedirs(dirname)
            open(full_path, 'ab').close()

    @api.autovacuum
    def _gc_file_store(self):
        """ Perform the garbage collection of the filestore. """
        assert isinstance(self, IrAttachment)
        if self._storage() != 'file':
            return

        # Continue in a new transaction. The LOCK statement below must be the
        # first one in the current transaction, otherwise the database snapshot
        # used by it may not contain the most recent changes made to the table
        # ir_attachment! Indeed, if concurrent transactions create attachments,
        # the LOCK statement will wait until those concurrent transactions end.
        # But this transaction will not see the new attachements if it has done
        # other requests before the LOCK (like the method _storage() above).
        cr = self._cr
        cr.commit()

        # prevent all concurrent updates on ir_attachment while collecting,
        # but only attempt to grab the lock for a little bit, otherwise it'd
        # start blocking other transactions. (will be retried later anyway)
        cr.execute("SET LOCAL lock_timeout TO '10s'")
        try:
            cr.execute("LOCK ir_attachment IN SHARE MODE")
        except psycopg2.errors.LockNotAvailable:
            cr.rollback()
            return False

        self._gc_file_store_unsafe()

        # commit to release the lock
        cr.commit()

    def _gc_file_store_unsafe(self):
        # retrieve the file names from the checklist
        checklist = {}
        for dirpath, _, filenames in os.walk(self._full_path('checklist')):
            dirname = os.path.basename(dirpath)
            for filename in filenames:
                fname = "%s/%s" % (dirname, filename)
                checklist[fname] = os.path.join(dirpath, filename)

        # Clean up the checklist. The checklist is split in chunks and files are garbage-collected
        # for each chunk.
        removed = 0
        for names in self.env.cr.split_for_in_conditions(checklist):
            # determine which files to keep among the checklist
            self.env.cr.execute("SELECT store_fname FROM ir_attachment WHERE store_fname IN %s", [names])
            whitelist = set(row[0] for row in self.env.cr.fetchall())

            # remove garbage files, and clean up checklist
            for fname in names:
                filepath = checklist[fname]
                if fname not in whitelist:
                    try:
                        os.unlink(self._full_path(fname))
                        _logger.debug("_file_gc unlinked %s", self._full_path(fname))
                        removed += 1
                    except (OSError, IOError):
                        _logger.info("_file_gc could not unlink %s", self._full_path(fname), exc_info=True)
                with contextlib.suppress(OSError):
                    os.unlink(filepath)

        _logger.info("filestore gc %d checked, %d removed", len(checklist), removed)

    @api.depends('store_fname', 'db_datas', 'file_size')
    @api.depends_context('bin_size')
    def _compute_datas(self):
        if self._context.get('bin_size'):
            for attach in self:
                attach.datas = human_size(attach.file_size)
            return

        for attach in self:
            attach.datas = base64.b64encode(attach.raw or b'')

    @api.depends('store_fname', 'db_datas')
    def _compute_raw(self):
        for attach in self:
            if attach.store_fname:
                attach.raw = attach._file_read(attach.store_fname)
            else:
                attach.raw = attach.db_datas

    def _inverse_raw(self):
        self._set_attachment_data(lambda a: a.raw or b'')

    def _inverse_datas(self):
        self._set_attachment_data(lambda attach: base64.b64decode(attach.datas or b''))

    def _set_attachment_data(self, asbytes):
        for attach in self:
            # compute the fields that depend on datas
            bin_data = asbytes(attach)
            vals = self._get_datas_related_values(bin_data, attach.mimetype)

            # take current location in filestore to possibly garbage-collect it
            fname = attach.store_fname
            # write as superuser, as user probably does not have write access
            super(IrAttachment, attach.sudo()).write(vals)
            if fname:
                self._file_delete(fname)

    def _get_datas_related_values(self, data, mimetype):
        checksum = self._compute_checksum(data)
        try:
            index_content = self._index(data, mimetype, checksum=checksum)
        except TypeError:
            index_content = self._index(data, mimetype)
        values = {
            'file_size': len(data),
            'checksum': checksum,
            'index_content': index_content,
            'store_fname': False,
            'db_datas': data,
        }
        if data and self._storage() != 'db':
            values['store_fname'] = self._file_write(data, values['checksum'])
            values['db_datas'] = False
        return values

    def _compute_checksum(self, bin_data):
        """ compute the checksum for the given datas
            :param bin_data : datas in its binary form
        """
        # an empty file has a checksum too (for caching)
        return hashlib.sha1(bin_data or b'').hexdigest()

    @api.model
    def _same_content(self, bin_data, filepath):
        BLOCK_SIZE = 1024
        with open(filepath, 'rb') as fd:
            i = 0
            while True:
                data = fd.read(BLOCK_SIZE)
                if data != bin_data[i * BLOCK_SIZE:(i + 1) * BLOCK_SIZE]:
                    return False
                if not data:
                    break
                i += 1
        return True

    def _compute_mimetype(self, values):
        """ compute the mimetype of the given values
            :param values : dict of values to create or write an ir_attachment
            :return mime : string indicating the mimetype, or application/octet-stream by default
        """
        mimetype = None
        if values.get('mimetype'):
            mimetype = values['mimetype']
        if not mimetype and values.get('name'):
            mimetype = mimetypes.guess_type(values['name'])[0]
        if not mimetype and values.get('url'):
            mimetype = mimetypes.guess_type(values['url'].split('?')[0])[0]
        if not mimetype or mimetype == 'application/octet-stream':
            raw = None
            if values.get('raw'):
                raw = values['raw']
            elif values.get('datas'):
                raw = base64.b64decode(values['datas'])
            if raw:
                mimetype = guess_mimetype(raw)
        return mimetype or 'application/octet-stream'

    def _postprocess_contents(self, values):
        ICP = self.env['ir.config_parameter'].sudo().get_param
        supported_subtype = ICP('base.image_autoresize_extensions', 'png,jpeg,bmp,tiff').split(',')

        mimetype = values['mimetype'] = self._compute_mimetype(values)
        _type, _, _subtype = mimetype.partition('/')
        is_image_resizable = _type == 'image' and _subtype in supported_subtype
        if is_image_resizable and (values.get('datas') or values.get('raw')):
            is_raw = values.get('raw')

            # Can be set to 0 to skip the resize
            max_resolution = ICP('base.image_autoresize_max_px', '1920x1920')
            if str2bool(max_resolution, True):
                try:
                    img = False
                    if is_raw:
                        img = ImageProcess(values['raw'], verify_resolution=False)
                    else:  # datas
                        img = ImageProcess(base64.b64decode(values['datas']), verify_resolution=False)

                    w, h = img.image.size
                    nw, nh = map(int, max_resolution.split('x'))
                    if w > nw or h > nh:
                        img = img.resize(nw, nh)
                        quality = int(ICP('base.image_autoresize_quality', 80))
                        image_data = img.image_quality(quality=quality)
                        if is_raw:
                            values['raw'] = image_data
                        else:
                            values['datas'] = base64.b64encode(image_data)
                except UserError as e:
                    # Catch error during test where we provide fake image
                    # raise UserError(_("This file could not be decoded as an image file. Please try with a different file."))
                    _logger.info('Post processing ignored : %s', e)
        return values

    def _check_contents(self, values):
        mimetype = values['mimetype'] = self._compute_mimetype(values)
        xml_like = 'ht' in mimetype or ( # hta, html, xhtml, etc.
                'xml' in mimetype and    # other xml (svg, text/xml, etc)
                not 'openxmlformats' in mimetype)  # exception for Office formats
        force_text = xml_like and (
            self.env.context.get('attachments_mime_plainxml') or
            not self.env['ir.ui.view'].sudo(False).check_access_rights('write', False))
        if force_text:
            values['mimetype'] = 'text/plain'
        if not self.env.context.get('image_no_postprocess'):
            values = self._postprocess_contents(values)
        return values

    @api.model
    def _index(self, bin_data, file_type, checksum=None):
        """ compute the index content of the given binary data.
            This is a python implementation of the unix command 'strings'.
            :param bin_data : datas in binary form
            :return index_content : string containing all the printable character of the binary data
        """
        index_content = False
        if file_type:
            index_content = file_type.split('/')[0]
            if index_content == 'text': # compute index_content only for text type
                words = re.findall(b"[\x20-\x7E]{4,}", bin_data)
                index_content = b"\n".join(words).decode('ascii')
        return index_content

    @api.model
    def get_serving_groups(self):
        """ An ir.attachment record may be used as a fallback in the
        http dispatch if its type field is set to "binary" and its url
        field is set as the request's url. Only the groups returned by
        this method are allowed to create and write on such records.
        """
        return ['base.group_system']

    name = fields.Char('Name', required=True)
    description = fields.Text('Description')
    res_name = fields.Char('Resource Name', compute='_compute_res_name')
    res_model = fields.Char('Resource Model', readonly=True)
    res_field = fields.Char('Resource Field', readonly=True)
    res_id = fields.Many2oneReference('Resource ID', model_field='res_model',
                                      readonly=True)
    company_id = fields.Many2one('res.company', string='Company', change_default=True,
                                 default=lambda self: self.env.company)
    type = fields.Selection([('url', 'URL'), ('binary', 'File')],
                            string='Type', required=True, default='binary', change_default=True,
                            help="You can either upload a file from your computer or copy/paste an internet link to your file.")
    url = fields.Char('Url', index='btree_not_null', size=1024)
    public = fields.Boolean('Is public document')

    # for external access
    access_token = fields.Char('Access Token', groups="base.group_user")

    # the field 'datas' is computed and may use the other fields below
    raw = fields.Binary(string="File Content (raw)", compute='_compute_raw', inverse='_inverse_raw')
    datas = fields.Binary(string='File Content (base64)', compute='_compute_datas', inverse='_inverse_datas')
    db_datas = fields.Binary('Database Data', attachment=False)
    store_fname = fields.Char('Stored Filename', index=True, unaccent=False)
    file_size = fields.Integer('File Size', readonly=True)
    checksum = fields.Char("Checksum/SHA1", size=40, readonly=True)
    mimetype = fields.Char('Mime Type', readonly=True)
    index_content = fields.Text('Indexed Content', readonly=True, prefetch=False)

    def _auto_init(self):
        res = super(IrAttachment, self)._auto_init()
        tools.create_index(self._cr, 'ir_attachment_res_idx',
                           self._table, ['res_model', 'res_id'])
        return res

    @api.constrains('type', 'url')
    def _check_serving_attachments(self):
        if self.env.is_admin():
            return
        for attachment in self:
            # restrict writing on attachments that could be served by the
            # ir.http's dispatch exception handling
            # XDO note: this should be done in check(write), constraints for access rights?
            # XDO note: if read on sudo, read twice, one for constraints, one for _inverse_datas as user
            if attachment.type == 'binary' and attachment.url:
                has_group = self.env.user.has_group
                if not any(has_group(g) for g in attachment.get_serving_groups()):
                    raise ValidationError(_("Sorry, you are not allowed to write on this document"))

    @api.model
    def check(self, mode, values=None):
        """ Restricts the access to an ir.attachment, according to referred mode """
        if self.env.is_superuser():
            return True
        # Always require an internal user (aka, employee) to access to a attachment
        if not (self.env.is_admin() or self.env.user._is_internal()):
            raise AccessError(_("Sorry, you are not allowed to access this document."))
        # collect the records to check (by model)
        model_ids = defaultdict(set)            # {model_name: set(ids)}
        if self:
            # DLE P173: `test_01_portal_attachment`
            self.env['ir.attachment'].flush_model(['res_model', 'res_id', 'create_uid', 'public', 'res_field'])
            self._cr.execute('SELECT res_model, res_id, create_uid, public, res_field FROM ir_attachment WHERE id IN %s', [tuple(self.ids)])
            for res_model, res_id, create_uid, public, res_field in self._cr.fetchall():
                if public and mode == 'read':
                    continue
                if not self.env.is_system():
                    if not res_id and create_uid != self.env.uid:
                        raise AccessError(_("Sorry, you are not allowed to access this document."))
                    if res_field:
                        field = self.env[res_model]._fields[res_field]
                        if field.groups:
                            if not self.env.user.user_has_groups(field.groups):
                                raise AccessError(_("Sorry, you are not allowed to access this document."))
                if not (res_model and res_id):
                    continue
                model_ids[res_model].add(res_id)
        if values and values.get('res_model') and values.get('res_id'):
            model_ids[values['res_model']].add(values['res_id'])

        # check access rights on the records
        for res_model, res_ids in model_ids.items():
            # ignore attachments that are not attached to a resource anymore
            # when checking access rights (resource was deleted but attachment
            # was not)
            if res_model not in self.env:
                continue
            if res_model == 'res.users' and len(res_ids) == 1 and self.env.uid == list(res_ids)[0]:
                # by default a user cannot write on itself, despite the list of writeable fields
                # e.g. in the case of a user inserting an image into his image signature
                # we need to bypass this check which would needlessly throw us away
                continue
            records = self.env[res_model].browse(res_ids).exists()
            # For related models, check if we can write to the model, as unlinking
            # and creating attachments can be seen as an update to the model
            access_mode = 'write' if mode in ('create', 'unlink') else mode
            records.check_access_rights(access_mode)
            records.check_access_rule(access_mode)

    @api.model
    def _filter_attachment_access(self, attachment_ids):
        """Filter the given attachment to return only the records the current user have access to.

        :param attachment_ids: List of attachment ids we want to filter
        :return: <ir.attachment> the current user have access to
        """
        ret_attachments = self.env['ir.attachment']
        attachments = self.browse(attachment_ids)
        if not attachments.check_access_rights('read', raise_exception=False):
            return ret_attachments

        for attachment in attachments.sudo():
            # Use SUDO here to not raise an error during the prefetch
            # And then drop SUDO right to check if we can access it
            try:
                attachment.sudo(False).check('read')
                ret_attachments |= attachment
            except AccessError:
                continue
        return ret_attachments

    @api.model
    def _search(self, domain, offset=0, limit=None, order=None, access_rights_uid=None):
        # add res_field=False in domain if not present; the arg[0] trick below
        # works for domain items and '&'/'|'/'!' operators too
        disable_binary_fields_attachments = False
        if not any(arg[0] in ('id', 'res_field') for arg in domain):
            disable_binary_fields_attachments = True
            domain = [('res_field', '=', False)] + domain

        if self.env.is_superuser():
            # rules do not apply for the superuser
            return super()._search(domain, offset, limit, order, access_rights_uid)

        # For attachments, the permissions of the document they are attached to
        # apply, so we must remove attachments for which the user cannot access
        # the linked document. For the sake of performance, fetch the fields to
        # determine those permissions within the same SQL query.
        self.flush_model(['res_model', 'res_id', 'res_field', 'public', 'create_uid'])
        query = super()._search(domain, offset, limit, order, access_rights_uid)
        query_str, params = query.select(
            f'"{self._table}"."id"',
            f'"{self._table}"."res_model"',
            f'"{self._table}"."res_id"',
            f'"{self._table}"."res_field"',
            f'"{self._table}"."public"',
            f'"{self._table}"."create_uid"',
        )
        self.env.cr.execute(query_str, params)
        rows = self.env.cr.fetchall()

        # determine permissions based on linked records
        all_ids = []
        allowed_ids = set()
        model_attachments = defaultdict(lambda: defaultdict(set))   # {res_model: {res_id: set(ids)}}
        for id_, res_model, res_id, res_field, public, create_uid in rows:
            all_ids.append(id_)
            if public:
                allowed_ids.add(id_)
                continue
            if not res_id and (self.env.is_system() or create_uid == self.env.uid):
                allowed_ids.add(id_)
                continue
            if not (res_field and disable_binary_fields_attachments) and res_model and res_id:
                model_attachments[res_model][res_id].add(id_)

        # check permissions on records model by model
        for res_model, targets in model_attachments.items():
            if res_model not in self.env:
                allowed_ids.update(id_ for ids in targets.values() for id_ in ids)
                continue
            if not self.env[res_model].check_access_rights('read', False):
                continue
            # filter ids according to what access rules permit
            ResModel = self.env[res_model].with_context(active_test=False)
            for res_id in ResModel.search([('id', 'in', list(targets))])._ids:
                allowed_ids.update(targets[res_id])

        # filter out all_ids by keeping allowed_ids only
        result = [id_ for id_ in all_ids if id_ in allowed_ids]

        # If the original search reached the limit, it is important the
        # filtered record set does so too. When a JS view receive a
        # record set whose length is below the limit, it thinks it
        # reached the last page. To avoid an infinite recursion due to the
        # permission checks the sub-call need to be aware of the number of
        # expected records to retrieve
        if len(all_ids) == limit and len(result) < self._context.get('need', limit):
            need = self._context.get('need', limit) - len(result)
            more_ids = self.with_context(need=need)._search(
                domain, offset + len(all_ids), limit, order, access_rights_uid,
            )
            result.extend(list(more_ids)[:limit - len(result)])

        return self.browse(result)._as_query(order)

    def write(self, vals):
        self.check('write', values=vals)
        # remove computed field depending of datas
        for field in ('file_size', 'checksum', 'store_fname'):
            vals.pop(field, False)
        if 'mimetype' in vals or 'datas' in vals or 'raw' in vals:
            vals = self._check_contents(vals)
        return super(IrAttachment, self).write(vals)

    def copy(self, default=None):
        if not (default or {}).keys() & {'datas', 'db_datas', 'raw'}:
            # ensure the content is kept and recomputes checksum/store_fname
            default = dict(default or {}, raw=self.raw)
        return super(IrAttachment, self).copy(default)

    def unlink(self):
        if not self:
            return True
        self.check('unlink')

        # First delete in the database, *then* in the filesystem if the
        # database allowed it. Helps avoid errors when concurrent transactions
        # are deleting the same file, and some of the transactions are
        # rolled back by PostgreSQL (due to concurrent updates detection).
        to_delete = set(attach.store_fname for attach in self if attach.store_fname)
        res = super(IrAttachment, self).unlink()
        for file_path in to_delete:
            self._file_delete(file_path)

        return res

    @api.model_create_multi
    def create(self, vals_list):
        record_tuple_set = set()

        # remove computed field depending of datas
        vals_list = [{
            key: value
            for key, value
            in vals.items()
            if key not in ('file_size', 'checksum', 'store_fname')
        } for vals in vals_list]

        for values in vals_list:
            values = self._check_contents(values)
            raw, datas = values.pop('raw', None), values.pop('datas', None)
            if raw or datas:
                if isinstance(raw, str):
                    # b64decode handles str input but raw needs explicit encoding
                    raw = raw.encode()
                values.update(self._get_datas_related_values(
                    raw or base64.b64decode(datas or b''),
                    values['mimetype']
                ))

            # 'check()' only uses res_model and res_id from values, and make an exists.
            # We can group the values by model, res_id to make only one query when
            # creating multiple attachments on a single record.
            record_tuple = (values.get('res_model'), values.get('res_id'))
            record_tuple_set.add(record_tuple)

        # don't use possible contextual recordset for check, see commit for details
        Attachments = self.browse()
        for res_model, res_id in record_tuple_set:
            Attachments.check('create', values={'res_model':res_model, 'res_id':res_id})
        return super().create(vals_list)

    def _post_add_create(self):
        pass

    def generate_access_token(self):
        tokens = []
        for attachment in self:
            if attachment.access_token:
                tokens.append(attachment.access_token)
                continue
            access_token = self._generate_access_token()
            attachment.write({'access_token': access_token})
            tokens.append(access_token)
        return tokens

    @api.model
    def create_unique(self, values_list):
        ids = []
        for values in values_list:
            # Create only if record does not already exist for checksum and size.
            try:
                bin_data = base64.b64decode(values.get('datas', '')) or False
            except binascii.Error:
                raise UserError(_("Attachment is not encoded in base64."))
            checksum = self._compute_checksum(bin_data)
            existing_domain = [
                ['id', '!=', False],  # No implicit condition on res_field.
                ['checksum', '=', checksum],
                ['file_size', '=', len(bin_data)],
                ['mimetype', '=', values['mimetype']],
            ]
            existing = self.sudo().search(existing_domain)
            if existing:
                for attachment in existing:
                    ids.append(attachment.id)
            else:
                attachment = self.create(values)
                ids.append(attachment.id)
        return ids

    def _generate_access_token(self):
        return str(uuid.uuid4())

    def validate_access(self, access_token):
        self.ensure_one()
        record_sudo = self.sudo()

        if access_token:
            tok = record_sudo.with_context(prefetch_fields=False).access_token
            valid_token = consteq(tok or '', access_token)
            if not valid_token:
                raise AccessError("Invalid access token")
            return record_sudo

        if record_sudo.with_context(prefetch_fields=False).public:
            return record_sudo

        if self.env.user.has_group('base.group_portal'):
            # Check the read access on the record linked to the attachment
            # eg: Allow to download an attachment on a task from /my/tasks/task_id
            self.check('read')
            return record_sudo

        return self

    @api.model
    def action_get(self):
        return self.env['ir.actions.act_window']._for_xml_id('base.action_attachment')

    @api.model
    def _get_serve_attachment(self, url, extra_domain=None, order=None):
        domain = [('type', '=', 'binary'), ('url', '=', url)] + (extra_domain or [])
        return self.search(domain, order=order, limit=1)

    @api.model
    def regenerate_assets_bundles(self):
        self.search([
            ('public', '=', True),
            ("url", "=like", "/web/assets/%"),
            ('res_model', '=', 'ir.ui.view'),
            ('res_id', '=', 0),
            ('create_uid', '=', SUPERUSER_ID),
        ]).unlink()
        self.clear_caches()
